Neurodegenerative diseases impart costs on individuals and society in terms of loss of function, costs of care, and the personal loss of identity associated with pain and suffering. Such diseases or cognitive disorders include, but are not limited to Alzheimer's Disease, Dementia with Lewy Body, Parkinson's Disease, and Progressive Supranuclear Palsy.
Cognitive impairment is a serious neurological condition which is very common in the elderly. It is estimated that approximately one-third of people who live to be over 80 years of age will be diagnosed with some form of cognitive impairment, or dementia. Cognitive impairment can result from a variety of disease processes, such as, but not limited to:
Neurodegenerative Dementia:                Alzheimer's Disease        Pick's Disease        Progressive Supranuclear Palsy        Dementia with Lewy Bodies        Parkinson's Disease        Fronto-temporal Dementia        
Vascular Diseases:                Stroke        Multi-infarct dementia        Subarachnoid hemorrhage        
Head Trauma
Infections:                Post-encephalitic dementia        Syphilis        Herpetic encephalitis        
Congenital Abnormalities:                Trisomy 21        
Toxic Brain Injuries:                Wernike Encephalopathy        Krorsakoff psychosis        Alcoholic amnesic syndrome        Alcoholic dementia        
The primary result of this general condition is a universal decline in the intellectual function of the individual, usually resulting in significant impediments to normal daily functions. While there is currently no disease modifying therapy available for most forms of cognitive impairment, certain treatments are available to treat the symptoms and improve cognitive functioning to varying degrees, which can alleviate or at least delay the need for institutionalizing these individuals.
It has been determined that the decline of the neurotransmitter chemical acetylcholine in the brain is one of the primary mechanisms of declining mental function. Medications that can prevent or at least minimize the breakdown of acetylcholine in the brain provide significant improvement in the cognitive abilities of patients diagnosed with cognitive impairment. These medications are commonly referred to as acetyl-cholinesterase inhibitors. However, as with any medication, there are side effects. For example, acetyl-cholinesterase inhibitors exacerbate urinary and fecal incontinence in patients administered these drugs. Other side effects include a reduced heart rate, sweating, vasodilation and increased bronchial secretions. Such side effects may be so uncomfortable for many elderly patients that the patient is unable to tolerate effective dosing of acetyl-cholinesterase inhibitors to successfully treat the cognitive impairment.
Attempts to ameliorate these undesirable side effects in cognitively impaired patients include the administration of, for example, antimuscarinic anti-cholinergic drugs (commonly called “anti-muscarinics”). These drugs block the peripheral stimulation of the acetylcholine receptors. Unfortunately, however, the use of these medications to treat the side effects of acetyl-cholinesterase inhibitors mentioned previously often contribute to cognitive impairment, which is what is being treated by the acetyl-cholinesterase inhibitor in the first place. Thus, benefits of using these drugs must be balanced with the risks of exacerbating the existing cognitive impairment. As a result, many patients are either inadequately treated or go untreated.
Over the years, researchers have studied the cognitive effects of anti-cholinergic drugs and have found that anti-cholinergic muscarinic drugs cause cognitive decline in the elderly and further cognitive decline in those already impaired. In fact, many practitioners refer to the dilemma regarding treatment of impairments in cognitive function in combination with incontinence as choosing between “your brain versus your bladder”. When prescribing medications, a practitioner has to work with their patients and their families and often decide whether to treat the incontinence caused by the medications being used to try to improve cognitive function, which would result in further detriment of cognitive function, or instead rely on alternative solutions to incontinence issues (including the often embarrassing use of adult diapers, or even institutionalization of the incontinent patient).
In addition to cognitive impairment, a more severe problem often afflicts the elderly and is referred to as acute delirium. The primary indicators are a pronounced change in mental status that rapidly fluctuates, the inability to maintain normal degrees of attention, disorganized thinking and vacillating levels of consciousness. Acute delirium can often result from a severe medical illness, recent surgery and use of several medications or interactions between various medications. The impact of acute delirium on patients is severe and often chronic, frequently leading to death.
While the neurological mechanism by which acute delirium occurs is not completely understood, like cognitive impairment, the neurotransmitter acetylcholine is thought to play a significant role. In patients suffering from dementia, a decline in acetylcholine has been seen in post mortem studies. As with treatments for cognitive impairment, the use of acetyl-cholinesterase inhibiting medications has been determined to prevent, to varying degrees, the breakdown of acetylcholine in the brain. However, the undesired side effects outside the central nervous system (CNS) that have been discussed above often result. In order to minimize these problems, the administration of drugs that block the peripheral effects of acetyl-cholinesterase inhibitors act would be desirable. Unfortunately, in a manner similar to other cognitive impairments, anti-cholinergics frequently contribute to the underlying problem by causing central nervous system toxicity.
There is thus a severe need to treat patients suffering from various forms of cognitive impairment as well as those suffering from acute delirium with an effective amount of medication to minimize or entirely alleviate these conditions without imposing upon them the undesired peripheral effects discussed previously, especially urinary and/or fecal incontinence, nausea, bradychardia, bronchorrhea and/or bronchospasm which often coexist with these cognitive impairments. The desire is to be able to administer the most efficacious type and amount of medication to treat the neurological condition without increasing the unwanted side effects of high doses of those medications. This balance has yet to be achieved in modern clinical practice.
There is also a need for treatments that alter the disease progression of progressive dementias and other cognitive impairments.